Various types of aspirated smoke detectors are known. One example is disclosed in U.S. Pat. No. 7,493,816 entitled, “Smoke Detectors” which issued Feb. 24, 2009. Another is disclosed in published US Patent Application 2009/0025453 entitled “Apparatus and Method of Smoke Detection” published Jan. 29, 2009. Both the '816 patent and the published '453 application are assigned to the assignee hereof and incorporated herein by reference.
Aspirated smoke detectors usually need a careful balance between sensitivity and nuisance rejection. Such detectors usually supervise a pretty wide area: in case of a fire, only a few holes in the aspirating pipe will be exposed to smoke/gas whilst most of the pipe still sucks clean air. So a large and unpredictable dilution effect will occur. Since the system must take in account the high dilution effect, high sensitivity—usually laser based—optical systems, are employed to maintain early fire detection in such conditions. This tends to limit the suitability of aspirated systems to clean environments such as computer rooms, telecommunication rooms or the like.
There is a need for aspirated detectors which might be usable in a broader range of environments.